How to Repair a Damaged Electrical Wire – Part 1

This project explains how to repair a damaged electrical wire by splicing in a new section of NM-B 14/2 wire with junction boxes.

The 120VAC wire splice fix is illustrated in the following diagram:

NM 14-2 Electrical Wire Repair Splice Diagram

This splice repair technique is useful for fixing damage when there’s not enough slack in the electrical cable to rejoin the ends together with wire nuts in a single junction box. For example, if a squirrel or rodent has a chewed through an electrical cable in the attic, or in my case, I also had to reroute the wire to correct a building code violation.

How to Repair a Damaged Electrical Wire

Damaged Electrical Wire and Building Code Violation

This run of 120VAC Romex NM 14/2 (Non-Metallic 14 gauge, 2 conductor with ground wire) electrical cable in the finished basement has several problems:

National Electrical Code (NEC) violation because it’s hanging unsupported outside the 2×4 studs. An example of sloppy work by the former homeowner.

The insulation has been cut on both the outer sheath and inner hot wire conductor then wrapped with electrical tape which is a improper repair method.

Damaged NM-B 14/2 Electrical Wire and Building Code Violation

Close-up of the damaged insulation. My guess is the the goober who installed the cable planned to cut it but changed his mind. It doesn’t explain why the hot wire (black) insulation is exposed. If you’re going to cut a wire, you don’t need to hack away at the insulation.

NM 14/2 Wire – Damaged Insulation

NM 14/2 Wire Splice Repair

The house electrical wire is repaired by:

Cutting the cable in two at the damaged area.

Rerouting the upper portion of the cable inside the crawlspace and 2×4 wall studs to correct the building code violation.

Splicing in a new span of NM 14/2 wire with two junction boxes.

The result is shown in this photo:

Repaired NM 14/2 Wire with Junction Boxes and Splice

A keen eye will note the black cable crossing in front of the 2×4 studs at the top right corner in the above photo – that’s the cable TV coaxial cable. I wouldn’t have routed it that way, however it’s not a safety or code problem.

NM-B 14/2 Electrical Cable Repair Parts and Tools

Two flush mount 4″ square by 1.5″ deep electrical junction boxes are required to splice in the repair span of NM 14/2 electrical cable. There are two types of steel electrical boxes:

with built-in cable clamps (left box in photo below)

without cable clamps (right box in photo below)

4″ Steel Electrical Box with Cover and NM Cable Clamps

For this repair I only needed the box with built-in cable clamps, although I used both types because I happened to have a box without clamps left over from a prior job. If you buy a box without clamps or need to bring in wires from another direction, the 1/2″ NM Cable Connectors are necessary to secure the wire in the knockout hole.

The parts are inexpensive, the electrical box with internal clamps cost $1.19 and a box cover is only 57 cents.

The steel junction boxes must be grounded but do not include the ground screw, so I bought a 10-pack of #10-32 green ground screws for $1.31. The #10-32 ground screw fits the smaller hole near the center of the steel electrical box.

Halex 10-32 Green Ground Screw

Closeup of the how the 14/2 NM electrical wire and NM Cable Connector are installed in the steel junction box. To install the cable, remove the 1/2″ inner knockout, attach the cable connector and lock nut, insert the wire and tighten the clamp screws until the cable is snug.

4″ Electrical Junction Box with 1/2″ NM Cable Connector

Knockouts are the several dimpled circles in the box sides. To remove a knockout, just hit it near the inner edge with the tip of a screw driver then bend it back and forth until the disc tab breaks.

A box of Romex NM 14/2 electrical wire, wire nuts and cable staples are needed. You can buy Romex in 25, 50 and 100 foot length boxes and coils at the home improvement store. Copper wire is getting expensive to rising metal prices, so only buy the minimum length of wire needed for your repair.

Romex NM 14/2 Wire, Wire Nuts and Cable Staples

I used the following tools in this electrical wire repair job:

Cordless drill/driver to attach the junction boxes to the 2×4 studs with wood screws

Diagonal cutting pliers

Needle nose pliers with cutter (you can get by with this only if you don’t have #2)

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6 Comments

I live in an apartment, and it looks like the painters for my complex cut the wires from one of the cable companies between the last tenant and me. There is a quarter inch of wire, at most, at the base of the wall, but we do not use the cable box. So is this an issue? The box (installed by Verizon in the past) does not look to be turned on, but do I need to do anything, or is OK since it’s out of use? Thanks.

The RG-6 coax cable only carries radio frequency (RF) signals with no significant voltage or current, so it’s normally nothing to be concerned about.

You could contact either the cable company or your landlord to request the cable be repaired. The cable company will probably defer responsibility to your landlord because the inside cable is the responsibility of the building owner. The cable company would probably repair it as a courtesy if you signed up for high-speed Internet, TV or phone service.

Hi. I have a 14/2 wire coming from the house and feeding an outdoor receptacle in the soffit. A rodent chewed through only the white insulation. The insulation on both wires is intact. Can I simply wrap the wire with electrical tape or do I need to cut and splice it?

Wrapping the wire with 600 volt rated electrical tape is probably what many people would do but it’s not compliant with the NEC. And you may have a problem if a home inspector flags the repair when you sell the house. Wiring a junction box is not difficult and well worth the piece of mind.

Rodents often enter the attic through the “carpenter’s gap” between the roof deck and fascia board. Use drip edge flashing to cover the carpenter’s gap. It’s inexpensive material and can be retrofitted on an existing roof. I had families of squirrels nesting in my attic insulation before the drip edge was installed.

Hello! Great article, very helpul! Can I leave the junction box hidden between drywall? I read in another article that is against code to leave the boxes hidden.

Still finding diffcult to understand that part on the NEC. It basically defeats the purpose of the repair. Damage caused by screws, nails or cutting a hole on the drywall will basically leave a mark (box cover) forever. A metallic (and even nowadays PVC) boxes will further protect the junction, even better than the rest of the wire running aroud the house that will remain more exposed to accidental damage than would be the wires/junctions inside the box. Does anybody knows why NEC requires even this kind of boxes to never be covered by drywall? Aren’t there anyway junctions boxes (hexagonal or round) unexposed around the house used by builders to distribute the cuircuits?

There are several options for making junction boxes more cosmetically appealing: * Install a finished plastic box cover. Paint or cover it with wallpaper to match. * Surface mount using WireMold. * Install an access panel so the box is accessible.